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The clinical manifestations of pneumococcal disease depend on the site of infection and the duration of illness.
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Pneumococcal pneumonia—the most common serious pneumococcal syndrome—is difficult to distinguish from pneumonia of other etiologies on the basis of clinical findings.
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Pts often present with fever, abrupt-onset cough and dyspnea, and sputum production.
– Pts may also have pleuritic chest pain, shaking chills, or myalgias.
– Among the elderly, presenting signs and symptoms may be less specific, with confusion and malaise but without fever or cough.
On physical examination, adults may have tachypnea (>30 breaths/min) and tachycardia, crackles on chest auscultation, and dullness to percussion of the chest in areas of consolidation.
– In some cases, hypotension, bronchial breathing, a pleural rub, or cyanosis may be present.
– Upper abdominal pain may be present if the diaphragmatic pleura is involved.
Pneumococcal pneumonia is generally diagnosed by Gram’s staining and culture of sputum.
– While culture results are awaited, chest x-rays—which classically demonstrate lobar or segmental consolidation—may provide some adjunctive evidence, although they may be normal early in the course of illness or with dehydration.
– Blood cultures are positive for pneumococci in <30% of cases.
– Leukocytosis (>15,000/μL) is common; leukopenia is documented in <10% of cases and is associated with a fatal outcome.
– A positive pneumococcal urinary antigen test has a high predictive value among adults, in whom the prevalence of nasopharyngeal colonization is low.
Empyema occurs in <5% of cases and should be considered when a pleural effusion is accompanied by fever and leukocytosis after 4–5 days of appropriate antibiotic therapy. Pleural fluid with frank pus, bacteria, or a pH of ≤7.1 indicates empyema and requires aggressive drainage.
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S. pneumoniae is among the most common causes of meningitis in both adults and children. Pneumococcal meningitis can present as a primary syndrome or as a complication of other pneumococcal conditions (e.g., otitis media, infected skull fracture, bacteremia). Pneumococcal meningitis is clinically indistinguishable from pyogenic meningitis of other etiologies.
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Pts have fever, headache, neck stiffness, photophobia, and occasionally seizures and confusion.
On examination, pts have a toxic appearance, altered consciousness, bradycardia, and hypertension (indicative of increased intracranial pressure). Kernig’s or Brudzinski’s sign or cranial nerve palsies (particularly of the third and sixth cranial nerves) are noted in a small fraction of adult pts.
Diagnosis of pneumococcal meningitis relies on examination of CSF, which reveals an elevated protein level, elevated WBC count, and reduced glucose concentration. The etiologic agent can be specifically identified by culture, antigen testing, or PCR. A blood culture positive for S. pneumoniae in conjunction with clinical manifestations of meningitis is also considered confirmatory.
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Other Invasive Syndromes
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S. pneumoniae can affect virtually any body site and cause invasive syndromes, including bacteremia, osteomyelitis, septic arthritis, endocarditis, pericarditis, and peritonitis. The essential diagnostic approach is collection of fluid from the site of infection by sterile technique and examination by Gram’s staining, culture, and—when relevant—capsular antigen assay or PCR. Hemolytic-uremic syndrome can complicate invasive pneumococcal disease.
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Noninvasive Syndromes
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Sinusitis and otitis media are the two most common noninvasive syndromes caused by S. pneumoniae; the latter is the most common pneumococcal syndrome and most often affects young children. See Chap. 58 for more detail.
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TREATMENT: PNEUMOCOCCAL INFECTIONS
Penicillin remains the cornerstone of treatment for pneumococcal disease caused by sensitive isolates, with daily doses ranging from 50,000 U/kg for minor infections to 300,000 U/kg for meningitis. Macrolides and cephalosporins are alternatives for penicillin-allergic pts but otherwise offer no advantage over penicillin.
Strains resistant to β-lactam drugs are increasing in frequency, and antibiotic recommendations are typically based on the minimal inhibitory concentration against the isolate, particularly in cases of invasive disease.